Wetter winters could be forecast months ahead.
American Geophysical Society Meeting, San Francisco, December 2001
Pressure system secrets could help long range forecasts.
The rise in levels of greenhouse gases has halted an oscillation of air pressures over the Arctic, bringing warmer, wetter winters to Northern Europe, Siberia and Alaska. The shift could get worse with increasing CO2 emissions, delegates heard this week at the American Geophysical Union meeting in San Francisco, California.
Scientists used to think that the AO was completely random. But in 1995 James Hurrell of the National Center for Atmospheric Research in Boulder, Colorado, showed that it actually follows a 10-year cycle and that since the 1980s the seesaw has been stuck in its positive phase1. "This has an impact on winter surface temperatures," says Hurrell.
Recent estimates suggest that the skewed AO may account for half of the warmer winter episodes and rainfall in northern Atlantic areas such as Scotland.
Working with the computer models used to forecast Britain’s weather, Gillett calculated the impact of a doubling of atmospheric CO2 levels (expected to happen by about 2040) on the AO’s intensity. He found that the additional CO2 would keep the AO in its positive phase and strengthen its effects.
Most experts agree that the skewed AO is probably caused by greenhouse gases, according to climatologist John Wallace at the University of Washington in Seattle. Although he cautions that climate models are never perfect.
What happens to the AO in the absence of man-made perturbations, on the other hand, is open to debate. One suggestion is that increasing tropical ocean temperatures cause the phenomenon. Another proposes that long-term cycles high in the stratosphere, six to thirty miles above the Earth, are driving it.
New evidence presented at the meeting by Mark Baldwin, of Northwest Research Associates in Bellevue, Washington, suggests that fluctuations in the stratosphere’s thickness are linked to the AO.
Although the effects of the stratosphere will still be amplified by an increase in greenhouse gases, the finding is otherwise good news, says Wallace, because the frequency of the waves are known. "These stratosphere waves could make 60-day forecasts possible," he says.
What’s more, longer-term fluctuations in tropical Atlantic temperature contribute to the power of stratospheric waves, so it should be possible to predict weather seasons in advance, says Wallace. "One day we might be predicting the likelihood of a certain number of cold snaps in the coming year," he says.
TOM CLARKE | © Nature News Service
Wandering greenhouse gas
16.03.2018 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung
Unique Insights into the Antarctic Ice Shelf System
14.03.2018 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung
Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...
On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...
The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...
At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.
When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...
At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.
Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...
16.03.2018 | Event News
13.03.2018 | Event News
08.03.2018 | Event News
16.03.2018 | Earth Sciences
16.03.2018 | Physics and Astronomy
16.03.2018 | Life Sciences